The invention is directed to a communication network in which message signals are transmitted, the network having a plurality of interconnected nodes.
The demands that operators and users of networks currently make with respect to quality and dependability in the transmission and switching of information require extremely reliable network components. Particularly lines and nodes, including the respective implemented software, must meet high standards for this reason and are redundantly implemented for dependability reasons.
Individual components are doubly provided in the prior art for establishing the redundancy in the networks. The doubling occurs at the level of the components, such as, for example, the lines, switching networks and control computers. Which of these redundantly implemented components are also involved in the transmission and switching function is decided by a local or central control. The advantage of such an apparatus is that the individual components can be examined individually, and the control of the implementation of the redundancy, especially of the components of the node, can ensue decentrally. Thus, a relatively simple hot standby mode can be implemented.
What is disadvantageous about such an apparatus, however, is that the distributed decision about the use of the redundancy requires a relatively high outlay that is customized for the employment. Since, moreover, the software in redundantly designed equipment is the same, the same software errors can occur in the two apparatuses. A further disadvantage of these structures is that cost-beneficial network node components cannot be utilized therein, since these components (readily available at present) do not have any redundancy. Let what are referred to as CPE components (customer promises equipment) be cited as an example thereof.